Data Recovery Case File · Portable Drives · Doing the Arithmetic

A day per gigabyte: the drive that would eventually mount — and the four months of copying it was offering

The customer had discovered, through patience bordering on heroism, a ritual that half-worked: plug the failed 1TB external into his Mac, leave it for a few hours, and sometimes one of its two partitions — the one with his files, mercifully, rather than the Time Machine backups — would appear in Finder. Then the real price emerged: opening a folder took an age, and transferring data ran at roughly a day per gigabyte. He had 120GB to save. That's four months of continuous copying, offered by a drive visibly dying — and the arithmetic, once stated, was the whole case for stopping.

The enquiry

“It won't mount when I plug it in. First Aid keeps giving an error — 'File system verify or repair failed (-69845)'. Sometimes if I plug it in and leave it a few hours, the partition with my files will mount and I can see them in Finder — but any operation takes a very long time, and transferring runs at about a day per gigabyte. I have about 120GB in the files partition.”

What the ritual was actually measuring

Each element of his routine was the same fault at a different magnification. A drive that needs hours to mount is spending those hours fighting through its own start-up reads against decayed surfaces — the same negotiation, at agonising length, that healthy drives complete in seconds. First Aid's -69845 was macOS attempting its checks against media that couldn't sustain them and reporting the surrender in a code. And the day-per-gigabyte crawl was the failure measured with a stopwatch: every block a struggle of retries, the throughput arithmetic of a drive reading almost nothing at almost every attempt. The trap in his discovery is its seduction — the partition does mount, the files are visible, so surely persistence wins? But four months of maximum-effort reading is not a rescue plan; it's a schedule for finishing the drive, with the odds of surviving to gigabyte 120 approximately nil. The visible files were real. The route to them wasn't.

The rescue, at the right layer

What takes a computer a day per gigabyte through a struggling drive's front door takes purpose-built hardware a different order of time through the side entrance. Behind the USB Stabilizer, the PC-3000 resolved the hours-long mounting battle at its source — the drive's degraded working structures repaired, its self-maintenance stood down — and Data Extractor imaged the drive with its priorities set by his own words: the files partition first, mapped through the filesystem so his 120GB led the queue, banked from the healthiest surfaces at proper speed; the Time Machine partition gathered afterwards as the lower-stakes second act. Bounded timeouts replaced the Mac's patient waiting; weak regions were revisited across passes instead of stalling the line. The files partition came off the image effectively complete and verified — the same 120GB Finder had been dangling, delivered inside the week rather than inside the season.

Outcome

Full practical recovery of the files partition, the backup partition's contents recovered behind it for good measure — and the arithmetic left standing as the page's takeaway. When a drive's transfer rate collapses by orders of magnitude, multiply it out: the number you get is not a plan, it's a diagnosis wearing units. A copy that maths out in months is a drive asking for a lab; the version of persistence that saves data is the one that stops persisting through the front door.

Our case files are drawn from genuine enquiries received by our laboratory over the past ten years, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery procedure our engineers apply to that fault, using the equipment listed.